Liquid pump and meter



Aug. 11, 1964 3,143,969

J. o. EAMES ET AL f LIQUID PUMP AND METER Filed May 11, 1961 s sheets-sheet 1 JAMES OWEN EAMES ROY S. SANFORD ATTORNEY AUgl-l 1964 J. o. EAMES E-rAL 3,143,969

LIQUID PUMP AND METER I Filed May 11, 1961 3 Sheets-Sheef. 2

JAMES OWEN EAMES ROY S. SANFORD ATTORNEY Aug. 11,1964

Filed May 11, ,1961

l .1. o. EAMES ET AL LIQUID PUMP AND METER 3 Sheets-Sheet 3 JAMES OWEN EAMES ROY S, SANFORD BY r- ATTORNEY United States Patent 3,143,969 LIQUID PUMP AND METER James Owen Eames, Washington, and Roy S.' Sanford, Woodbury, Conn., assignors to Roy S. Sanford & Coml pany, Oxford, Conn., a partnership Filed May 11, 1961, Ser. No. 109,406 11 Claims. (Cl. 10s-42) This invention relates to pumps, and more particularly to liquid pumps. Y

In connection with pumps for liquid, diiculty is often experienced due to the presence of entrained air and vapor in the liquid discharged from the pump, and itis accordingly one of the objects of the invention to provide means for automatically eliminating such air andvapor whenever the pump is operating.

Another object of the invention is to provide, in a pump of the above type, means for accurately measuring the amount of liquid pumped from the discharge.

A further object of the invention -is to provide simple and eicient means for controlling the operation of such a pump in accordance with the demand for liquid from the pump.

Still another object of the invention is to provide novel valve means for a pump of the above type.

Yet another object of the invention is to provide an electrically driven pump adapted for use as a fuel pump for an internal combustion engine. Y

Another object of the invention is to provide a cam operated pump mechanism, together with means for accurately recording the amount of liquid pumped.

These and other objects of the invention will be more clearly understood when considered in therlight of the following description and the appended claims.

In the drawings, wherein similar reference numerals refer to similar parts throughout the several views;

FIG. l is a sectional View -of a pump incorporating the principles of the invention;

FIG. 2 shows a modification of the invention in section, and fFIG. 3 is a sectional view of another modification.

Referring first to FIG. 1, showing a liquid pump constructed in accordance with the principles of the invention, the pump includes a pump housing 4 having a crankcase portion 5 at its right end closed by -a cover plate 6, and a cylinder bore 7 closed at its left by means of a cylinder head 8 and its right end by means of a wall 9 having a piston rod bore 10 extending therethrough from the cylinder into the crankcase. A differential piston 11 is slidably mounted in the cylinder bore and has a piston rod12 at its right end extending through the piston rod bore l0 into the crankcase, the rod being sealed against leakage by a suitable seal 13.

The driving means for the piston includes a crank shaft 14 having a crank 15 and a crank pin 16 thereon connected to the piston rod by means of a connecting rod 17 and a pivot pin 18 on the piston rod. An electric motor 19 is mounted on the outside of the housing with a motor shaft 20 extending into the crankcase portion of the housing and provided with a drive pinion 21 which meshes with a crankshaft gear 22 secured to the crankshaft. Since the piston is driven by a crankshaft, the travel of 4the piston in either direction is fixed at all times, and consequently in the event the liquid pumped is uncontaminated by entrained air or vapor, the number of revolutions of the crankshaft in 'a given period of time gives an accurate indication of the amount of liquid pumped, and in the present instance such indication may be given by means of a suitable counter 23 mounted on the outer surface of the end plate 6 and connected to the crankshaft by means of a shaft `24 and suitable bevel gears or other means, not shown.

3,143,969 Patented Aug. 11., 1964 The piston divides the cylinder into a suction chamber 25 at the left end of the piston and a pumping chamber 26 at the right end `of the piston, and in View of the fact a differential piston is utilized, the change in volume in the suction chamber is always greater than the change of volume in the pumping chamber 26 whenever the piston is moved in the cylinder. The cylinder is provided with an inlet port 27 normally closed by an inlet valve 28 loaded by an intake valve spring 29, a liquid return port `30 normally closed by a return valve 31 held in closed position by a spring 32, and a discharge valve port 33 having a discharge valve 33a normally held closed by a discharge valve spring 34 interposed between the valve and a ported plate 35. The piston is provided with ports 36 extending therethrough, as well as with a flexible piston cup 37 of suitable material, the lip of the cup extending toward the pumping chamber 26. i

It will be understood from the foregoing, that on movement of the piston to the right by the operation of the crankshaft, liquid will be vdrawn from a supply into the suction chamber 25 through the inlet valve 28, While at i the same time, any liquid or fluid presen-t in the pumping chamber 26 will tend to be compressed by the action of the piston cup acting as -a seal and will be discharged through the discharge valve port 33, and it will also be noted that the displacement in chamber 25 during a complete stroke of the piston to the right will be much greater than the displacement in pumping chamber 26 dueto the use of the differential piston. When the piston moves to the left, liquid in suction chamber 25 will be forced past the flexible packing cup 37 and through the ports 36 into the pumping chamber 26 in order to maintain the latter chamber filled during the stroke of the piston to the left. However, the amount of liquid in the suction chamber 25 will be more than suflicient to lill the pumping chamber 26, and consequently the excess, including any entrained Iair or vapor which may have been drawn in from the liquid supply during the suction stroke will be pumped out of the return port past the return valve 31 and returned to the supply, the lines to the supply being connected at 3S. In order to accomplish the above type of operation, tension of the return valve spring 32, the exhaust valve spring 34, and the tension or stiffness of the lip of the piston cup 37 are so correlated that during the movement of the piston to the left when liquid is bypassing the piston into the pumping chamber 26, the pressure can never become sufficient to open the discharge valve to permit the escape of' liquid therethrough. However, the spring 32 is so designed that the return valve 31 can open during movement of the pistonto the left and permit the excess liquid which was drawn into the suction chamber to be -returned to the supply through the return valve. On movement `of `the piston to the right, however, it will be clear that there is nothing to prevent opening of the discharge valve provided the electric motor is powerful enough to operate the piston to produce the necessary pressure.

In the event it is desired to use this pump as an electric fuel pump for an automotive engine, for example, the discharge is connected to the carburetor at outlet 39, a discharge chamber 40 being connected to the outlet by means of a passage 41. In order to automatically control the operation of the pump in accordance with the demand of the vehicle engine carburetor, motor terminal 42 is connected by wire 43 to the vehicle battery 44, While motor terminal 45 is connected by a wire 46 to terminal 47 of a snap action switch 48. Battery terminal 49 is connected through wire 50 land switch 51 as well as wire 52 with terminal 53 of the snap action switch 48, so that when the switch 51 is closed, the snap action switch 48 controls the operation of the motor.

The switch 48 is controlled by the pressure in the discharge line to the carburetor, the construction being such that when the pressure exceeds a certain amount, the motor is de-energized, and is again energized when the pressure drops to a lower predetermined value. To establish this control, an accumulator is mounted on the top part of the housing, this including a casing 55 and a flexible diaphragm 56 secured along its outer periphery between the lower end of the casing and the pumphousing 4. A diaphragm follower 56a engages the upper side of the diaphragm and has a switch operating rod 57 secured thereto. A spring 58 urges the diaphragm follower downward against the diaphragm, and the upper end of the rod is provided with a notch 59 adapted for engagement with lever 60 of the snapl action switch 48, the construction being such that on engagement of the rod at either end of the notch with the switch lever, a predetermined movement of the lever occurs before anything happens in the switch itself, at which time the switch contacts snap over to a dterent position, depending on whether the contacts were previously closed or opened. By properly adjusting the length of the notch and the construction of the snap action switch, the accumulator mechanism can be set to maintain the pressure in the line leading to the carburetor within a predetermined range at all times, and also insures against appreciable pulsations in the line leading tot the carburetor.

In the operation of a pump of the above type, it has been found that the force required to move the piston to the right during the pumping stroke is greater than that required to move the piston in the other direction, a fact which increases the torque requirements of the electric motor, and if desired, in order to even out the torque required of the motor during a complete cycle, a helper spring 61 may be interposed between the cylinder head and the left end of the piston so that the spring will be compressed during movement of the piston to the left, and will assist the motor in moving the piston to the right during the pumping stroke in order to permit the use of a slightly smaller motor.

Although the pump is shown with the cylinder horizontal, it may be desirable to operate it with the axis of the cylinder vertical and with the return port 30 at the top in order to more fully eliminate any entrained air and vapor and to prevent the possibility of such air and vapor being forced past the lip of the piston cup during the movement of the piston to the left. The position of the return valve may be changed as desired in order to facilitate more fully the elimination of air and vapor when the pump is operated in a different position from that shown.

In the event the pump is used to handle flammable liquids such as gasoline, or toxic liquids, it may be desirable to insure against any possible leakage from the 'pumping chamber into the crankcase past the piston rod seal, and such a feature as well as other novel features are included in the pump illustrated in FIG. 2.

As was the case in FIG. 1, the mechanism includes a crankcase 5 closed by an end plate 6 and a cylinder 7 closed at its left end by a cylinder head 8 and at its right end by a wall 9 having a bore 10 extending therethrough. In this construction, however, the crankcase is separate from the cylinder and is secured thereto as by means of cap screws 62. A piston 11 is slidably mounted in the cylinder and has a piston rod 12 of reduced diameter extending from the right side thereof, this rod extending through but spaced from the wall of the bore 10. In order to seal against any leakage from the pumping charnber 26 at the right end of the piston, a stocking type diaphragm 63 is utilized, the outer periphery of the diaphragm being clamped between the crankcase and the cylinder, and the inner peripheral portion of the diaphragm being clamped between the right end of the piston rod 12 and a piston guide 64 slidably mounted in a piston guide bore 65 in the crankcase.

v The piston is operated by means of a crank 15 having a crank pin 16 connected to the piston guide 64 by means of a connecting rod 17 and a pivot pin 18 on the piston guide, the piston guide being secured to the piston by means of a cap screw 66 as shown. The crankshaft is provided with a gear 22 which meshes with a pinion 21 on shaft 20 of an electric motor 19 mounted on the crankcase housing.

The piston divides the cylinder into a suction chamber 25 and a pumping chamber 26, the suction chamber having an inlet port 27 normally closed by a spring biased valve 28, and a return port 30 normally closed by a spring biased valve 31. A discharge port 33 is provided Y for the pumping chamber and this is normally closed by a spring biased valve 33a.

An accumulator 54 is provided similar to that shown in FIG. l, the accumulator including an accumulator casing 55 mounted on the upper portion of the cylinder member with a flexible diaphragm 56 clamped therebetween along its outer periphery. A diaphragm follower 56a rests against the upper surface of the diaphragm, being pressed thereagainst by means of a spring 58. As shown, the lower side of the diaphragm is subjected to the pressure in discharge chamber 40 through port 35a in the spring retaining plate 35. The upper end of a follower rod 57 is provided with a switch operating notch 59 adapted to engage the end of the switch operating lever 60. Motor terminal 42 is connected to switch terminal 53 through wire 43, battery 44, wire 50, switch 51 and wire 52, while terminal 45 of the motor is connected to the control switch terminal 47 through wire 46. Thus, when the switch 51 is closed, the pressure acting on the diaphragm 56 controls the operation of the snap action switch in order to control the operation of the motor in accordance with the pressure in discharge outlet 41, this portion of the operation being substantially the same as that occurring in the structure shown in FIG. 1.

In this embodiment of the invention, the counter 23 is of the remotely controlled magnetic type having terminals 67 and 68, the terminal 67 being connected by wire 69 to wire 43 leading to the battery, the battery in turn being connected to a terminal 70 on crankcase cover plate 6 through Vthe wire 50, the switch 51, and a wire 71. The other counter terminal 68 is connected to a terminal 72 on the crankcase cover plate by a wire 73, terminal 72 being connected to a resilient switch leaf 74 by wire 75, and terminal 70 being connected to a resilient switch leaf 76 by wire 76a. The switch leaves are provided respectively with contacts 77 and 78 which are normally open, and the left end of the switch leaf 75 is provided with a bent portion 79 adapted to be engaged by the outer end of the crank once during each revolution in order to make contact between the contacts 78 and 77 to energize the magnetic counter. It has been found in the operation of experimental pumps of this type that the piston never tends to stop at dead center at the right end of the stroke, and consequently the crank does not stop normally until it is past the switch leaf projection 79, thus insuring against the contacts 77 and 78 remaining closed for a prolonged period of time with detrimental eiects to the battery and to the counting mechanism. It will be understood that this mechanism can be incorporated in the structure of FIG. 1, or that conversely, the counter mechanism of FIG. 1 can be incorporated in FIG. 2 instead of the mechanism shown.

A unique feature of the structure shown in FIG. 2 resides in the arrangement for bypassing liquid from the suction chamber to the pumping chamber during movement of the piston to the left, and as shown in the drawing, such arrangement includes a U-shaped piston cup Si) which is ilexible and of well known construction, the cup being slidably mounted in the cylinder with the outer lip in engagement with the cylinder wall and the inner lip 80a in engagement with a cylindrical portion 81 of the piston, which blends into a portion of reduced diameter at 82 just to the right of the right hand edge of the lip. As will be seen, the piston'cup is mounted for limited axial movement relative to the piston, being located in one direction in the position shown in the drawing by a stop or llange 83 on the piston, and being adapted on limited relative movement in the opposite direction to be engaged and held against further movement in said direction by a stop ring 84 mounted on the piston rod for movement therewith. As shown, ports 85 are provided in the stop ring in order to insure the unrestricted passage of liquid by the ring from the left side to the right side during operation of the pump.

With the parts in the position shown, assuming that the switches 51 and 48 are closed, the crankshaft turns in a clockwise direction in order to move the piston to the right in the cylinder to draw liquid into the suction chamber 25 from a liquid supply through the inlet valve 28, and at the same to pump liquid to a carburetor or other liquid consuming device through the discharge valve 33a and the discharge outlet 39. Consequently due to the pressure in the pumping chamber 26, as well as the frictional engagement of the outer lip of the cup with the cylinder Wall, the cup rests as shown against the flange 83 on the piston and moves bodily with the piston during the pumping stroke. As the crankshaft passes dead center however, the frictional engagement of the outer lip of the cup of the cylinder wall tends to hold the cup stationary While the piston moves to theV left to take up the lost motion between the cup and the stop ring S4, and when this lost motion is taken up, the cylindrical portion 81 of the piston moves to the left relative to the inner lip of the cup sufficiently to clear the lip and allow free passage of liquid between the lip and the surface of the piston rod 12 which is of lesser diameter than the cylindrical portion 31, ports 86 being provided in the piston to insure the free passage of liquid to the left side of the cup when positioned against the stop ring. Thus, during movement of thepiston to the left, liquid is free to pass the piston to maintain the pumping chamber 26 filled with liquid, while at the same time, the excess liquid which was drawn in during the suction stroke into the chamber 25, since it cannot go into the pumping chamber 26, and since it cannot be discharged through the discharge valve 33a, because of the loading imparted thereto by the discharge valve spring, is returned to the supply through the return valve 31 and the connection at 38 which goes to the supply.

In the event a pump constructed in this manner is to be used as an accurate fuel meter, it is important that the proper relationship be maintained between the effective area of the diaphragm 63 and the area of the cylindrical portion 81 of the piston, as during relative movement of the piston cup and piston, it is possible for a change in volume to take place in the pumping chamber 26 unless the diaphragm and the cylindrical portion have the same effective diameter. It will be noted that in eiect the U-shaped piston cup acts as a valve, and that due to manufacturing tolerances and so forth, the point at which the inner lip of the cup engages or disengages cylindrical portion 81 may be indeterminate, and it is for this reason that a variation in volume can take place in the chamber 26 unless the two diameters in the two areas above referred to are substantially identical. The stocking type diaphragm shown is particularly adapted for use in this connection, since its effective area remains substantiallyconstant regardless of stroke within reasonable limits and can be readily computed. As was the case in FIG. l, it will be understood that the loading or biasing of the discharge valve relative to the loading of the return valve is such that during movement of the piston to the left, the pressure build up in pumping chamber 26 is insufficient to force open the discharge valve, but the pressure in the chamber 25 is suiicient to open the return valve 31. On the stroke to the right, the piston cup acts as a seal, and suliicient pressure is of course built up in the chamber 26 to open the discharge valve and to discharge a volume of liquid equal to the displacement of the piston during its stroke to the right, thus providing an accurate measure of the liquid pumped which can be recorded on a counter as shown if so desired. Any vapor or air which is entrained in the liquid entering 4the suction chamber through the intake valve during the suction stroke is thus discharged and returned to the liquid supply with the excess liquid in the chamber during the stroke of the piston to the left.

There has thus been provided a pumping unit which is sealed against leakage of flammable or toxic liquids, and which if desired can be used as an accurate device to meter the amount of liquid pumped for each complete cycle, and in addition in the event it is desired. to use this for a fuel pump for an automotive engine4 or the like, means are provided for accurately controlling the pressure in the discharge line leading to the engine carburetor.

Referring now to FIG. 3, a pump of this general type is shown wherein the pump is operated mechanically as by means of a cam on the cam shaft of a vehicle engine in somewhat the same manner as the conventional diaphragm type fuel pumps now used on engines of this type. As was the case in the other modifications, the structure includes a crankcase or cam case 5 closed by an end plate 6, a cylinder 7 closed at its left end `by a cylinder head 8 and at its right end by a wall 9 having a piston rod bore 10 therein. A piston 11 is slidably mounted in the cylinder and provided with a piston rod 12 extending to the right therefrom and slidably mounted in the bore 10, a seal 13 serving to prevent leakage at this point. The piston divides the cylinder into a suction chamber 25 and a pumping chamber 26, and leakage by the piston between these chambers is prevented by a suitable seal 87 carried by the piston. The cylinder is provided with inlet valve 28, return valve 31, and discharge valve 33a, all these valves being spring biased toward closed position in the same manner as previously described. The means for bypassing liquid from the suction chamber 25 to the pumping chamber 26 by the piston includes a bypass valve 88 biased toward closed position by a relatively light spring 89 and communicating through a port 90 with inlet chamber 90a. A chamber 91 at the right of this bypass valve is connected to the pumping chamber 26 through a bypass passage 92. Thus, on movement of the piston to the right, liquid is drawn from a supply into the suction chamber 25, and the liquid in the pumping chamber 26 is discharged through the discharge valve 33a, while on subsequent movement of the piston to the left, liquid is pumped from the suction chamber 25 through the bypass valve 88 and the bypass passage 92 to the pumping chamber 26 in an amount sui-licient to maintain that chamber full during the entire stroke to the left, the excess previously drawn intochamberl 25 above that necessary to maintain the chamber 26 filled being returned to the supply through the return valve 31 and a connection to the supply tank.

As stated heretofore, this particular embodiment of the pump is adapted to be operated mechanically by'a cam, for example on the cam shaft of an internal cornbustion engine, and such a cam is shown as being a cam 93 mounted for rotation with a cam shaft 94 which may be mechanically driven in any suitable manner. This cam cooperates with a tappet head 95 at the right end of the piston rod 12, movement of the piston to the rightrbeing effected by a compression spring 96 interposed between the right side of the wall 9 and the left side of the tappet head 95. The piston is positively moved to the left by the action of the cam 93.

It will be noted, however, that in this case, the stroke of the piston is not necessarily fixed, as in the event the pressure in the discharge line builds up to a point such that the spring 96 has insuflicient force to move the piston to the right, or in the event the discharge valve x piston to the right.

line is entirely closed momentarily, the tappet head 95 Will not follow the cam, and the stroke temporarily at least will be less than that for which the device is designed. In like manner, in the event the cam is operated at extremely high speeds, it may be that the spring will be unable to make the tappet head follow the cam resulting in a variation of stroke. Consequently in the event it is desired to use this pump as a meter to measure the amount of liquid pumped through the discharge, a different counter arrangement is required, and this is shown in the drawlng. Y

This counter mechanism measures the total stroke of the piston to the right only, regardless of the distance through which the piston moves at any one time. A counter shaft 97 is provided and connected to a suitable counter, not shown, a friction ratchet wheel 9S being secured to the shaft for rotation therewith. An actuating and pawl arm 99 is pivotally mounted on the shaft and is urged in a counterclockwise direction by means of a tension spring 100 interconnected between the lever and a pin 101 secured to the housing. The bottom end of the lever is provided with a portion 102 maintained against the left side of the tappet head 95 by the spring 100, while at the upper end a spring pressed friction pawl 103 is pressed into frictional engagement with the outer periphery of the wheel 9S by means of a spring 104. Thus, on movement of the piston and the tappet head to the right during the pumping stroke under the influence of the spring 96, the lever 99 will rotate in a counterclockwise direction and by virtue of the engagement of the pawl 103 with the periphery of the ratchet wheel, will rotate the wheel in a counterclockwise direction through an angle proportional to the degree of movement of the In the event the piston and tappet head is now moved to the left by the action of the cam, the lever will move in a clockwise direction, and the pawl 103 will slide along the surface of the wheel without moving it, although in order to insure against retrograde movement, a pawl brake is provided comprising a bell crank shaped pawl 105 maintained in frictional engagement with the surface of the wheel 98 by means of a suitable spring 106, and serving effectively to prevent rotation of the Wheel in a clockwise direction during clockwise rotation of the lever 99.

It will be seen from the foregoing that the operation of this pump is very similar to that obtaining in the well known diaphragm type engine driven fuel pump used on many automobile engines, and that in addition means are provided for eliminating entrained air and vapor and for utilizing such a pump as a meter to accurately measure the amount of fuel used if so desired. It is also to be understood that the cam shaft 94 may be driven by any suitable means such as an electric motor, and that such motor may be controlled by an accumulator controlled switch.

There has thus been provided by the present invention, simple and effective means for pumping volatile and other liquids uncontaminated by entrained Vapor and air, and means which can be readily adapted if desired, and as shown in the drawings, as an accurate liquid meter for determining the amount of liquid pumped during any given period of time. Such pumps serve a very useful purpose in connection with the testing of the fuel consumption of automobiles and internal combustion engines as well as in many other applications where an accurate measure of the liquid pumped is desired, and the pump is particularly useful in connection with the pumping of very volatile fuels which tend to vaporize readily when subjected to reduced pressure during the intake stroke of the pump.

Although the invention has been illustrated and described in considerable detail, it is to be understood that other modifications may well suggest themselves to those skilled in the art, and that the invention is not to be considered as limited except as set forth in the appended claims. Reference will, therefore, be had to the appended claims for a definition of the limits of the invention.

What is claimed is:

1. A pump for liquid including a suction chamber having an inlet valve and a return valve, said chamber being adapted to receive liquid from a liquid supply through the inlet valve and to return a portion of the liquid to the supply through the return valve, a pumping chamber having a discharge valve, means connecting said chambers including a one-way valve for conducting liquid from the suction chamber to the pumping chamber, movable differential liquid displacing means associated with said chambers movable in one direction to draw liquid into said suction chamber from a supply and to discharge liquid from the pumping chamber through said discharge valve and movable in the opposite direction to transfer a portion of the liquid drawn into the suction chamber to said pumping'chamber through said connecting means and to return the rest of the liquid so drawn in to the liquid supply through said return valve, said displacing means being so constituted with respect to said chambers that on movement of the Adisplacing means a given distance the change in volume eifected thereby in the suction chamber exceeds the change in volume effected thereby in the pumping chamber by a predetermined amount, and means for biasing said intake, return and exhaust valves toward closed position, the biasing means being so constituted as to prevent opening of the discharge valve by the pressure in the pumping chamber and to permit opening of the return valve by the pressure in the suction chamber when the liquid displacing means is moving in said opposite direction.

2. A liquid pump as set forth in claim l, including a discharge line connected to the pumping chamber through the discharge valve, power operated means having a connection with the liquid displacing means for moving the latter, and means responsive to the pressure in the discharge line for controlling the energization of the power operated means.

3. A liquid pump as set forth in claim l, including indicating means for indicating the volume of liquid discharged from said pumping chamber during a given period of time, said indicating means including an indicator having an operative connection with the liquid displacing means, the indicator and operative connection being so constituted as to indicate the total travel of the displacing means in said one direction during said period.

4. A liquid pump as set forth in claim 1, including a crankshaft having an operative connection with said liquid displacing means, said crankshaft and operative connection being operable to reciprocate the displacing means with a fixed stroke, an electric motor connected to the crankshaft to rotate the shaft, means including a switch for controlling the energization of the motor, an expansible chamber connected to said pumping chamber through said discharge valve, and a switch operating member associated with said expansible chamber movable in one direction by the pressure in said expansible chamber and resiliently biased in the opposite direction, said switch operating member and switch being so arranged as to deenergize said motor when the pressure in said expansible chamber exceeds a predetermined value and to energize the motor when said pressure reaches a lower predetermined value.

5. A liquid pump including a cylinder, a differential piston slidaby mounted in the cylinder and dividing the latter into suction and pumping chambers, the change in volume in the suction chamber being greater than the change in volume of the pumping chamber during movement of the piston a given distance, an inlet valve for the suction chamber, means for conducting liquid from the suction chamber to the pumping chamber including a one-way valve, a discharge port in the pumping chamber, means for reciprocating the piston in the cylinder, the piston being operable on movement in one direction to draw liquid from a supply into the suction chamber through said inlet valve and to discharge liquid from the pumping chamber through said discharge port and operable on movement in the other direction to force liquid from the suction chamber into the pumping chamber through said conducting means to maintain the pumping chamber full of liquid, the volume of liquid drawn into the suction chamber during piston movement in said one direction being greater than that required to maintain the pumping chamber full of liquid during movement of the piston an equal distance in said other direction, and means operable during operation of the pump for eliminating entrained air and vapor from the liquid drawn into said suction chamber including a discharge valve for the discharge port, valve biasing means for urging the discharge valve to closed position against the pressure in the pumping chamber, a return port in the suction chamber adapted to be connected to the liquid supply, a return valve for the return port, and biasing means for urging said return valve to closed position against the pressure in the suction chamber, the biasing force of the discharge valve biasing means being so chosen as to prevent opening of the discharge valve by the pressure in said pumping chamber during movement of the piston in said other direction.

6. A liquid pump as set forth in claim 5, wherein the liquid conducting means includes a flexible packing cup secured to the piston adjacent the suction chamber with the lip of the cup extending toward the pumping chamber and being in engagement with the cylinder wall, the cup acting on movement of the piston in said one direction to prevent the passage of liquid between said chambers and the lip being forced away from the cylinder wall by the liquid on movement of the piston in said other direction to provide a passage for liquid from the suction chamber to the pumping chamber.

7. A liquid pump as set forth in claim 5, wherein the means for reciprocating the piston includes a rotatable crankshaft having a crank and a connection between the crank and the piston, the crank insuring a predetermined length of piston travel during each pumping cycle, and means for indicating the volume of liquid discharged from the pumping chamber including a counter having an operative connection with the crankshaft.

8. A liquid pump including a cylinder, a differential piston slidable therein and forming in conjunction therewith a closed suction chamber at one end thereof and a closed pumping chamber at the other end thereof, means for reciprocating the piston in the cylinder, means including a one-way valve for conducting liquid from the suction chamber to the pumping chamber, an inlet valve for the suction chamber, a return valve for the suction chamber, a discharge valve for the pumping chamber, and means for biasing said return and discharge valves to closed position against the pressures in the corresponding chambers, the discharge valve being biased to open at a pressure at least equal to that required to open the return valve, the inlet and return valves both being adapted to be connected to a liquid supply to respectively receive liquid from the supply and to return liquid from the suction chamber to the supply, and the discharge valve being adapted to be connected to a pump discharge line.

9. A liquid pump including a cylinder, a differential piston slidably mounted therein and forming in conjunction therewith a closed suction chamber at one end thereof and a closed pumping chamber at the other end thereof, an inlet valve for the suction chamber, a return valve for the suction chamber, a discharge valve for the pumping chamber, means for biasing the return valve and discharge valve to closed position against the pressures in the corresponding chambers, the discharge valve being biased to open at a pressure equal to or greater than that at which the return valve opens, means for reciprocating the piston in the cylinder to draw liquid from a supply into the suction chamber through said intake valve on movement of the piston in one direction and force a portion of said liquid into the pumping chamber on movement of the piston in the other direction, and means for preventing the flow of liquid between said chambers during movement of the piston in said one direction and for conducting liquid from the suction chamber to the pumping chamber during movement of the piston in the other direction including a exible packing cup mounted on the piston for limited axial movement with respect thereto with a lip of the cup in frictional engagement with the cylinder wall and directed toward the pumping chamber, a passage in the piston between the two chambers, and a seat for the cup on the piston, the cup being engageable with said seat during movement of the piston in said one direction to close said piston passage and the piston seat moving away from the cup to open the passage on movement of the piston in said other direction.

10. In combination with a cylinder body having a bore and a differential piston slidably mounted therein and forming, in conjunction with the cylinder, a closed chamber at either end of the cylinder, combined piston sealing and valve means for preventing the flow of fluid between the chambers during movement of the piston in one direction and for conducting fluid between the chambers during movement of the piston in the opposite direction, said means including a passage through the pistion, a cylindrical portion of lesser diameter than the cylinder formed on the piston in one of the chambers, a U-shaped flexible packing cup mounted on the piston and movable axially a limited distance with respect to the piston, the outer lip of the cup being in frictional and sealing engagement with the cylinder wall, and fixed stops on the piston of limiting the relative axial movement of the cup and piston, the inner lip of the cup being in sealing engagement with said cylindrical portion of the piston when the cup is in engagement with one of said stops and being out of engagement with said cylindrical portion when the cup is in engagement with the other of said stops.

1l. The combination set forth in claim 10, wherein an extension of said reduced portion of the piston extends outward through a bore in the end of the cylinder body, and the bore is sealed against leakage by a stockingtype diaphragm, the diaphragm being secured along its outer periphery to the cylinder body and along its inner periphery to the piston extension, and the effective area of the diaphragm being substantially the same as the cross sectional area of said cylindrical portion of reduced diameter on the piston.

References Cited in the tile of this patent UNITED STATES PATENTS 1,129,009 Petermoller Feb. 16, 1915 1,744,684 Grifl'ith Jan. 2l, 1930 2,696,785 Blue Dec. 14, 1954 2,761,391 Johnston Sept. 4, 1956 2,771,846 Horton et al. Nov. 27, 1956 2,808,786 Johnston Oct. 8, 1957 2,931,313 Hughes Apr. 5, 1960 2,968,255 Loeber Ian. 17, 1961 3,012,509 Mercier Dec. 12, 1961 3,023,936 Marsh et al. Mar. 6, 1962 

1. A PUMP FOR LIQUID INCLUDING A SUCTION CHAMBER HAVING AN INLET VALVE AND A RETURN VALVE, SAID CHAMBER BEING ADAPTED TO RECEIVE LIQUID FROM A LIQUID SUPPLY THROUGH THE INLET VALVE AND TO RETURN A PORTION OF THE LIQUID TO THE SUPPLY THROUGH THE RETURN VALVE, A PUMPING CHAMBER HAVING A DISCHARGE VALVE, MEANS CONNECTING SAID CHAMBERS INCLUDING A ONE-WAY VALVE FOR CONDUCTING LIQUID FROM THE SUCTION CHAMBER TO THE PUMPING CHAMBER, MOVABLE DIFFERENTIAL LIQUID DISPLACING MEANS ASSOCIATED WITH SAID CHAMBERS MOVABLE IN ONE DIRECTION TO DRAW LIQUID INTO SAID SUCTION CHAMBER FROM A SUPPLY AND TO DISCHARGE LIQUID FROM THE PUMPING CHAMBER THROUGH SAID DISCHARGE VALVE AND MOVABLE IN THE OPPOSITE DIRECTION TO TRANSFER A PORTION OF THE LIQUID DRAWN INTO THE SUCTION CHAMBER TO SAID PUMPING CHAMBER THROUGH SAID CONNECTING MEANS AND TO RETURN THE REST OF THE LIQUID SO DRAWN IN TO THE LIQUID SUPPLY THROUGH SAID RETURN VALVE, SAID DIS- 